It is missing only icons rewrite that will make icons (such as bell icon for notifications in header) clickable and some minor stuff.
You can find list of fixed/changed stuff here: https://github.com/phpbb/phpbb/pull/1803

Problem: when viewing forum icon to redirect to newest unread post is hard to click:
Chances of user hitting that icon are next to none because it is located right near topic link. So far I've come up with 2 solutions:

Make folder image clickable, redirecting to newest post for unread topics and latest post for read topics. Problem with this approach is it isn't intuitive. There is no way for users to know about it.

Change topic link for unread topics to link to first unread post on mobile devices. Change its color to indicate that it links to unread post, remove unread post icon. I think this is best approach so far because when users visit any topic, more often they want to see new posts than first post.